Server load balancing efficiently divides traffic to a plurality of servers which provide the same service to distribute workload of a server, which increases server availability and network bandwidth efficiency.
FIG. 1 shows a prior server load balancing.
In server load balancing in layer 4 (L4), as shown in (a) of FIG. 1, a load balancing apparatus determines which host a packet is transmitted to, with reference to information on the L4 included in the packet, that is, Internet protocol (IP) and port information.
Also, in server load balancing in layer 7 (L7), as shown in (b) of FIG. 1, a load balancing apparatus determines which host a packet is transmitted to, with reference to information on the L7 included in the packet, that is, payload information (for example, hypertext transfer protocol (HTTP) header information).
As in the L7, contents are divided and stored according to servers and server balancing is performed based on the payload information which is a domain of HTTP, a uniform resource locator (URL) path, a file extension, and others. Further, in the L4, a network address translation (NAT) method for performing load balancing based on the IP of a server and the port information is widely used.
Recently, the size of contents through a network has increased and the volume of contents has also increased, thereby there is a certain limit to manage the contents with a direct attached storage (DAS) structure in which a server stores the entire contents. Accordingly, a method in which an original server stores contents and a service server requests contents from the original server only when it is needed and provides the contents to a client is used. A method such as a network attached storage (NAS), a storage area network (SAN), an HTTP, and a file system is used for connection between an edge server and a storage unit.
However, the larger the number and the volume of contents is, the smaller the number of contents which are hit in a local disk or a memory of the edge server is, the larger the frequency of requesting contents from an original server is, and then the larger the load of the edge server is. Also, the number of cases in which the edge server requests contents from the original server increases, and thereby the load of the original server increases.